A standard helmet is known, for example from German utility model 8,306,006 which is secured to the wearer's head by a strap assembly comprising a pair of side straps each having a rear end attached in the back of the helmet and a front end attached at the temple region, and a chin strap passing from the center region of the one side strap to the center region of the opposite side strap. Normally fittings are provided on the side straps that allow attachment of the chin strap to the side straps and a releasable buckle or clasp is provided at one end of the chin strap to allow easy removal of the helmet.
In the known system the side straps are permanently fixed at their rear ends on the helmet, but are fitted to any of several different attachment location at the front temple region of the helmet so their lengths can be adjusted. In addition the fittings on the side straps where the chin strap is attached are of the self-binding type can slide easily when no tension is applied to them, but that cannot slide when the chin strap pulls on them.
As a result it is fairly difficult to adjust such a helmet. The ends of the side straps must both be set, and then the positions of both side-strap fittings. Finally the length of the chin strap must be set. Clearly such complicated adjustment is disadvantageous.